Phase contrast X-ray device for creating a phase contrast image of an object and method for creating the phase contrast image

ABSTRACT

The invention concerns a phase contrast X-ray device ( 1 ) for creating a phase contrast image of at least one object ( 4 ) with at least one X-ray source ( 2 ) for generating an X-radiation that has a specific spatial coherence ( 14 ) within a specific optical distance ( 6 ) to the X-ray source and at least one evaluation unit ( 16 ) for converting the X-radiation after the X-radiation has passed through the object arranged within the optical distance to the X-ray source in the phase contrast image of the object. The phase contrast X-ray device is characterized in that the X-ray source has an output ranging from 50 W up to and including 10 kW and a spatial coherence length of the X-radiation has been selected within the optical distance to the X-ray source ranging from 0,05 μm. This is obtained by using an X-ray source with line-shaped focus ( 7 ) and/or by monochromating the X-radiation by using a gradient multilayer reflector ( 20 ). With monochromating, the X-radiation has a temporal coherence ( 15 ) suitable for recording the phase contrast image of a thicker object. The X-ray device is suitable for use in medical technology and the non-destructive material testing.

[0001] The invention relates to a phase contrast X-ray device forcreating a phase contrast image of at least one object with at least oneX-ray source for generating an X-radiation that exhibits a specificspatial coherence within a specific optical distance to the X-ray sourceand at least one evaluation unit for converting the X-radiation afterthe X-radiation has passed through the object arranged within theoptical distance to the X-ray source in the phase contrast image of theobject. A method for creating a phase contrast image of an object byusing the phase contrast X-ray device is also described.

[0002] In the same way as in the visible light optical range, the X-rayoptical range must also convert a phase contrast to an amplitudecontrast to make a phase contrast object visible. Therefore, a phasecontrast image means a graphical representation of a phase contrastconverted to an amplitude contrast. However, images of objects areconsidered throughout in which the contrast image is actually based onphase contrast and not amplitude contrast.

[0003] The phase contrast radiography underlying the invention is basedon the fact that X-rays which pass through a phase contrast object, i.e.through adjacent ranges of different optical thickness, have awell-defined phase difference to one another. Therefore, these X-rayscan interfere with one another (X-ray interference). As a result of thisX-ray interference, an amplitude or intensity contrast image is observedat a sufficient distance. The interference is also related to adeflection of the radiation to the direction of incidence (diffraction).The above-mentioned phase contrast object can be seen as a transparentobject with one lateral variation of the thickness, the refractive indexor both. In contrast to the X-ray absorption radiography, an image of anobject can be generated with the phase contrast radiography which has alower absorption for X-rays and small absorption contrasts based on thethickness, the density or the element composition.

[0004] A phase contrast X-ray device of the kind mentioned at thebeginning and an appropriate method is e.g. known from Wilkins et al.,Nature, 384 (1996), pages 335-338 (cf. FIG. 2). The X-ray source of theknown X-ray device is point-shaped and has a very small diameter from 5μm to 15 μm. The evaluation unit is, for example, an X-ray film. Theobject to be investigated is arranged within the optical distance to theX-ray source between the point-shaped X-ray source and the evaluationunit. The optical distance results from a ray path of the X-radiation.Divergent X-rays radiated from the point-shaped X-ray source passthrough the object. At a phase limit of the object, a passing through ofthe object causes a phase shift of the X-radiation. Both phase-shiftedand non-phase shifted X-rays reach the evaluation unit, are converted toan amplitude contrast there and made visible as a so-called phasecontrast image.

[0005] Based on the smaller diameter of the point-shaped X-ray source ofthe known phase contrast X-ray device, a (radiographic) output of theX-ray source is restricted to below 50 W. Because of the lower output,the phase contrast X-ray device is suitable for creating a phasecontrast image of a thin, small object, for example an insect. The knownphase contrast X-ray device is not suitable for larger and thickerobjects, for example a human being, because of the lower output.Therefore, the phase contrast X-ray device is also not suitable for usein medical technology.

[0006] A monochromator as a gradient multilayer reflector is known fromSchuster et al., Proc. SPIE, 3767 (1999), pages 183-198. The gradientmultilayer reflector is an artificial, one-dimensional grid that allowsthe Bragg area of reflection of X-radiation. The reflector distinguishesitself by means of a periodic series of layers of a first layer type Aand a further layer type B. The first layer type A has a firstrefractive index r_(A) and a first layer thickness d_(A) and a furtherlayer thickness B, a further refractive index r_(B) and a layerthickness d_(B) differing from the first refractive index r_(A). In onelateral direction of propagation of the reflector, the layer thicknessesincrease by a total of d=d_(A)+d_(B). The gradient multilayer reflectorthen has an area of reflection that can be elliptical, parabolic,circular or planar.

[0007] The gradient multilayer reflector is used, for example, as amirror in X-ray diffractometry. By using this gradient multilayerreflector, parallel and nonparallel X-radiation of a relatively greatphoton energy bandwidth can be reflected and can be monochromated with arelatively small intensity loss.

[0008] The object of the present invention is to specify an improvedphase contrast X-ray device compared to the known prior art by means ofwhich a phase contrast image of a larger or thicker object can becreated. Another object is to specify an improved method for creating aphase contrast image compared to the known prior art.

[0009] In order to achieve the object of the invention, a phase contrastX-ray device is specified for creating a phase contrast image of atleast one object with at least one X-ray source for generating anX-radiation that has a specific spatial coherence within the specificoptical distance to the X-ray source and at least one evaluation unitfor converting the X-radiation after the X-radiation has passed throughthe object arranged within the optical distance to the X-ray source inthe phase contrast image of the object. The phase contrast X-ray deviceis characterized in that the X-ray source has an output ranging from 50W up to and including 10 kW and a spatial coherence length of theX-radiation has been selected within the optical distance to the X-raysource ranging from 0.05 μm up to and including 10 μm.

[0010] In order to achieve the further object of the invention, a methodfor creating a phase contrast image of an object by using the phasecontrast X-ray device is given with the following procedural steps:

[0011] a) Arranging the object within the optical distance to the X-raysource,

[0012] b) X-radiation passing through the object and

[0013] c) Creating the phase contrast image from where the X-radiationpasses through an object by means of the evaluation unit.

[0014] The object is characterized by at least one boundary surface thatcan be made visible with the phase contrast image. The boundary surfaceis, for example, formed by different, adjacent parts of the object.These parts can be, for example, different vessels of a plant or ananimal.

[0015] The evaluation unit features a detector for the X-radiationpassing through the object. The detector is, for example, an X-ray film.An X-ray tracer or an X-ray tracer carrier that converts the X-radiationinto visible light is also feasible. The phase contrast image is createdfrom the visible light.

[0016] The basic idea of the invention is to prepare a phase contrastX-ray device with an X-ray source for X-radiation in which case theX-radiation has an X-radiation within the optical distance to the X-raysource that is suitable for recording a phase contrast image of anobject. For that, the X-radiation has a specifically suitable spatialcoherence within the optical distance for recording a phase contrastimage. The spatial coherence also becomes a transversal coherence. Thespatial coherence length of the X-radiation is only a few μm within theoptical distance. Over and above this basic requirement for recording aphase contrast image, the X-ray source output must be selected in such away that it is between 50 W and 10 kW. Therefore, the output is higherthan that of the known phase contrast X-ray device. The phase contrastX-ray device is suitable for creating a phase contrast image of both asmaller object, for example, an insect and a larger object, for example,a human being. A recording period of the phase contrast image is alsoacceptable for larger objects. Therefore, the phase contrast X-raydevice can also be used in medical technology, for example, in alaboratory or a hospital. Using the phase contrast X-ray device inbotany, the semiconductor technology and the microstructure technologyis also feasible. For example, in semiconductor technology, a thinbonding wire of aluminum on a silicon chip could be shown. Applicationin safety engineering for testing a safety-relevant object is alsofeasible. The safety-relevant object is, for example, a bag whosecontents are to be shown by means of the phase contrast X-ray device.The contours of explosives or drugs could be rendered visible in thephase contrast image.

[0017] Measures based on special embodiments by means of which the basicidea of the invention is developed further are given below.

[0018] In a special embodiment, the X-ray source has a line-shapedfocus. The focus is elongated. A focus length of the focus isconsiderably greater than a focus width of the focus. The focus can thenalso have a rectangular focus area. An elliptical focus area is alsofeasible. For example, the focus width is only a few μm and the focuslength, on the other hand, is up to several mm. The line-shaped focusallows a considerably higher tube output and therefore a higherintensity than a comparable tube with point-shaped focus.

[0019] In a further embodiment, a longitudinal extension of theline-shaped focus is actually aligned in the direction towards theobject. The longitudinal extension is determined by the focus length.The direction of the object is given by the light path of theX-radiation from the X-ray source to the object. The alignment of thefocus is elongated. The elongated alignment guarantees a useable spatialcoherence length (cf. F. S. Crawford Jr., “Schwingungen und Wellen”(Oscillations and Waves) (Vieweg, Braunschweig, 1989), pages 259-271).

[0020] For example, an X-ray source is used together with a conventionalX-ray tube. The X-ray tube resembles a fine focus or finest focus fromX-ray diffractometry. In contrast to X-ray diffractometry, the alignmentof the line-shaped focus is elongated. For such a flat measurement, ananode roughness in the (sub)μm range is suitable.

[0021] In a special embodiment, the X-ray source has an X-ray tube witha transmission anode. The X-ray tube is a transmission X-ray tube. Forthis type of X-ray tube, the X-radiation is measured from the anode inthe direction of bombardment of the electrons—therefore, in transmission(cf. L. M. N. Tavora, E. J. Morton, W. B. Gilboy, SPIE vol 3771 (1999)61-71). Very often, in the case of transmission X-ray tubes, the anodeis used at the same time as the tube window.

[0022] In a special embodiment, the X-ray source has a parametricX-radiation source. The parametric X-radiation source is a veryefficient and powerful X-radiation source that can also be fitted in thedescribed X-radiation device. In the case of a parametric X-radiationsource, electrons are bombarded typically with 50 MeV into amonocrystalline anode material, e.g. graphite, diamond or beryllium.Therefore, X-radiation emerges that is considerably intensified if it ismeasured under the Bragg angle corresponding to the X-radiation.

[0023] Parametric X-radiation (PXR: parametric x-radiation, cf. M. A.Piestrup, Xizeng Wu, V. V. Kaplan, S. R. Uglov, J. T. Cremer, D. W.Rule, R. B. Fioroto, Rev. Sci. Intrum. 72 (2001) 2159-2170) is a type ofX-radiation from many different X-radiation types, the generationprocess of which is very similar, but the generation of which requiresdifferent operating parameters. These X-radiation types are, forexample, coherent X-radiation in crystals (CBS), Vavilov-Cerenkovradiation (VR), channeling radiation (CHR) and resonant radiation (RR)(cf. V. G. Baryshevsky, I. D. Feranchuk, Nucl. Instr. Meth. 228 (1985)490-495; W. Knupfer, M. G. Huber, Physik in unserer Zeit 6 (Physics inour time 6) (1984) 163-172). These types of X-radiation can be used inthe phase contrast X-ray device of this invention.

[0024] In addition to the X-ray sources described, an electron-excitedplasma X-ray source or a laser-excited plasma X-ray source (laserCompton scattering) is feasible (cf. A. Tsunemi et al. IEEE 3 (1999)926-927; A. Tsunemi et al. IEEE 4 (1999) 2552-2554).

[0025] In a further embodiment, the X-radiation of the phase contrastX-ray device displays a specific temporal coherence. The temporalcoherence is also designated as the longitudinal coherence ormonochromatism. Therefore, a temporal coherent X-radiation is amonochromatic X-radiation of a smaller bandwidth. In order to generatethe temporal coherence, the phase contrast X-ray device has at least onemonochromator. The monochromator filters X-radiation of a specific wavelength λ or a specific energy E from the polychromatic X-radiation ofthe X-ray source. The monochromator is arranged in the light path of theX-radiation between the X-ray source and the optical distance.Therefore, monochromatic X-radiation passes through the object. Thecoherence of the temporal X-radiation is particularly advantageous forcreating phase contrast images of thicker objects. Thicker objects areobjects whose extension in the direction of propagation of theX-radiation is clearly greater than the coherence length of theX-radiation. The coherence length is, for example, only a few μm and thethickness of the object, on the other hand, up to several mm or cm.

[0026] In order to be able to distinguish the phase shift of objectswith a thickness T from those with a multiple thickness T*n, thethickness is preferably less than λ/2δ. To prevent an ambiguity in theinterferences, it is advantageous if a fluctuation of the wave length λand the refractive index decrement δ is small.

[0027] The evaluation unit comprises at least a film or an X-raydetector with selective area analysis capabilities. The evaluation unitalso preferably has an analyzer for analyzing the direction ofpropagation after the X-radiation has passed through the object. Theanalyzer can then have a collimator. The analyzer particularly has amonochromator or resembles a monochromator. Whereas the wavelength ofthe photons is determined with a monochromator, the direction ofpropagation/collimation of the photons is determined with an analyzer.

[0028] In a special embodiment, the monochromator and/or analyzer has atleast one gradient multilayer reflector. The reflector distinguishesitself by means of a periodic series of layers of a first layer type Aand a further layer type B. The first layer type A has a firstrefractive index r_(A) and a first layer thickness d_(A) and a furtherlayer thickness B, a further refractive index r_(B) and a layerthickness dB differing from the first refractive index r_(A). In atleast one lateral direction of propagation of the reflector, the layerthicknesses increase by a total of d=d_(A)+d_(B). By using the gradientmultilayer reflector, parallel and non-parallel X-radiation can bemonochromated or collimated with a relatively small intensity loss. Thegradient multilayer reflector then has an area of reflection that can beelliptical and/or parabolic and/or planar and/or circular. The area ofreflection either curves in only one direction of propagation or in twopropagation directions of the gradient multilayer reflector. Because anarea of reflection curves in two propagation directions of the gradientmultilayer reflector it is possible not to only deflect the radiation inthe plane of the arriving X-radiation, but also to change the plane ofthe reflecting X-radiation. Therefore, a spatial focusing can beobtained.

[0029] A spatial coherence needed to record the phase contrast imagecan, in particular, be accessed by using the gradient multilayerreflector. By using the reflector, the light path in which the object isarranged can be developed in parallel or divergently. A divergent lightpath can be obtained with a planar area of reflection. In the case of anelliptical or circular area of reflection, a focused light path isobtained. A parabolic area of reflection collimates the light path, i.e.the X-rays run in parallel.

[0030] In particular, another monochromator as a gradient multilayerreflector is used as an analyzer. The analyzer is suitable for a specialembodiment of the invention after an X-radiation which is deflected whenpassing through the object for creating a phase contrast image and/or anX-radiation which is non-deflected when passing through the object isdetected. The deflected and/or non-deflected X-radiation is selected bymeans of an analyzer with a gradient multilayer reflector. For example,at the reflector only the non-deflected X-radiation is guided in thedirection of the detector of the evaluation unit.

[0031] In a special embodiment, the X-radiation forms an interferencepattern after it has passed through the object that is detected forcreating the phase contrast image. The interference pattern, forexample, is recorded on an X-ray film.

[0032] In a special embodiment, several phase contrast images arecreated by means of the X-radiation of different spatial coherences thatare processed to an overall phase contrast image by means of an imageprocessing unit. For example, the individual phase contrast images aredigitized and then converted by the image processing unit into theoverall phase contrast image. It is also feasible that the individualphase contrast images are recorded with a single X-ray film and aresuperimposed onto an overall phase contrast image in this way.

[0033] A greater coherence length brings about a stronger diffractioneffect and allows a higher phase contrast and sharper boundaries.However, complicated object structures can superimpose the diffractionpatterns of different object structures that are difficult to interpret.For a smaller coherence length, the phase contrast is less and, on theother hand, the phase contrast of specific object structures can beallocated in a simpler manner. Without image processing, phase contrastimages with greater coherence lengths can possibly no longer bedetermined. However, image processing programs also supply artifacts ifa phase contrast image should be processed with a greater coherencelength. Therefore, a repetitive evaluation algorithm is proposed inwhich the rough contours/boundaries of the object structures are firstof all recorded in images with smaller coherence lengths and then thesecontours/boundaries are refined by means of images with a greatercoherence length.

[0034] The optical distance between the object and the X-ray sourcepreferably varies for generating the different spatial coherence. Thespatial coherence length is then enlarged in both dimensions to the sameextent with the distance.

[0035] As an alternative, orientation of the object to the direction ofpropagation of the X-radiation varies for generating the differentspatial coherence. For example, the object is rotated in the case of anunchanged light path. One requirement for this is an anisotropy of thespatial coherence length, i.e. that the spatial coherence length differsin the two transversal directions.

[0036] It is indeed also feasible that the object remains laboratoryproof, but that the anisotropic alignment is turned at an angle, by forexample varying the two lateral extensions of the X-ray source. Thefocus and therefore also an X-ray source form can be changed in an X-raytube.

[0037] This method preferably uses an object that, in essence, consistsof a material with a low absorption coefficient for the X-radiation.Such an object or a part of the object cannot be shown directly, i.e. byusing X-ray absorption. This object or a part of the object can be anysoft part of humans, an animal or a plant. The soft part, for example,is a vessel of a body fluid of an animal. Organs that are not in aposition to record a radioopaque medium needed to directly create anX-ray absorption image can, in particular, also be shown by means of thevisualized phase contrast X-ray devices. Such organs are, for example,cartilages or periosteum.

[0038] In a further embodiment, many phase contrast images of the objectare recorded to create a phase contrast computer tomogram of the object.Although the phase contrast X-ray radiography can also generate asufficient contrast when there is no absorption contrast, the localdetails—as is customary for a projection technology—can only be shownsuperimposed. The method of computer tomography overcomes this problem:The object to be tested is scanned linearly and turned at slight anglesthroughout the process. A transversal sector tomogram is then generatedfrom the position and angle-dependent intensities according to thewell-known process of computer tomographic reconstruction.

[0039] Summarizing, the Following Exceptional Advantages Result FromThis Invention:

[0040] Based on the higher tube output, this phase contrast X-ray devicepresented can, in particular, be used in medical technology for showingthe soft parts of larger objects.

[0041] By using an X-ray source with line-shaped focus and/or by usingone or several gradient multilayer reflectors, the intensity of theX-radiation within the optical distance increases or is used moreefficiently.

[0042] Via the shape and alignment of the X-ray source, the spatialcoherence of the X-radiation suitable for creating a phase contrastimage can be ensured.

[0043] By using the gradient multilayer reflector, monochromating andalso the temporal coherence of the X-radiation can be obtained withsmall intensity losses. Based on the temporal coherence, the phasecontrast images of thicker objects can be accessed.

[0044] A gradient multilayer reflector, in particular, is used as ananalyzer. With the reflector, the X-radiation that has passed throughthe object can be analyzed in a simple way.

[0045] Based on several examples and the appropriate figures, the phasecontrast X-ray device and the method for creating the phase contrastimage of an object is shown by means of the phase contrast X-ray device.The figures are diagrammatic and do not display images to scale.

[0046]FIG. 1 shows the cross-section of a phase contrast X-ray devicewith an X-ray source with line-shaped focus.

[0047]FIG. 2 shows the cross-section of a phase contrast X-ray deviceknown from the state of the art.

[0048]FIG. 3 shows the cross-section of a gradient multilayer reflector.

[0049]FIG. 4 shows the light path of a phase contrast X-ray device witha monochromator as a gradient multilayer reflector with a planar area ofreflection.

[0050]FIG. 5 shows the light path of a phase contrast X-ray device witha monochromator and an analyzer each in the form of a gradientmultilayer reflector with a planar area of reflection.

[0051]FIG. 6 in each case shows the light path of a phase contrast X-raydevice with a monochromator and an analyzer each in the form of agradient multilayer reflector with a bent area of reflection.

[0052]FIG. 7 shows a method for creating a phase contrast image by meansof the phase contrast X-ray device.

[0053] The phase contrast X-ray device 101 known from the state of theart that is described in the introduction is shown in FIG. 2. Taking thepoint-shaped X-ray device 2 as a starting basis, the divergent X-rays 11arrive at the object 4 arranged within the optical distance 6 to theX-ray source 2. After the X-radiation 11 has passed through the object4, non-deflected, deflected and X-radiation 12 and 13 arrive at anevaluation unit 16 as an X-ray film by means of which the phase contrastimage is generated. In order to obtain sufficient coherence length 15for recording a phase contrast image, the diameter of the point-shapedX-ray source 2 is restricted and therefore the output of the X-raysource 2 is also limited to a maximum of 50 W.

[0054] On the other hand, the output of X-ray source 2 of this phasecontrast X-ray device 1 exceeds 50 W. By means of the phase contrastX-ray device 1, a phase contrast image of an object 3 is created in eachcase. The object is cartilage on a bone. For that, the object 3 isarranged within the optical distance 6 to the X-ray source 2 (FIG. 7,71). The object distinguishes itself with boundary surfaces 5 that canbe shown by means of phase contrast radiography. After arranging,X-radiation passes through the object (FIG. 7, 71) and the phasecontrast image is created from the X-radiation passing through theobject by means of the evaluation unit 16. The evaluation unit 16 alsohas an X-ray film by means of which the X-radiation is detected. A phasecontrast image is created.

[0055] In an embodiment of the method for creating the phase contrastimage, the spatial coherence of the X-radiation used is changedgradually by varying the optical distance (FIG. 7, 74). In this way,several phase contrast images are created with X-radiation havingdifferent spatial coherence. These different phase contrast images aredigitized and processed by means of an image processing unit into anoverall phase contrast image.

[0056] According to a further embodiment of the method, many phasecontrast images are generated by turning the object. A phase contrasttomogram is created from the many phase contrast images via an imageprocessing device.

[0057] The way in which the output of the X-ray source 2 of the phasecontrast X-ray device 1 can be increased and an image quality of thephase contrast image that can be created with this, can be increased, isdescribed below. In essence, two routes are then followed: According tothe first route, the phase contrast X-ray device 1 is equipped with anX-ray source 2 with line-shaped focus 7 (example 1). The second routeprovides an optical system in the light path to optimize the radiationintensity and the spatial coherence 14 and, if required, the temporalcoherence 15 of the X-radiation 11 (examples 2 to 7).

EXAMPLE 1

[0058] Phase contrast X-ray device 1 with X-ray source 2 withline-shaped focus 7 (FIG. 1).

[0059] The X-ray source 2 has a line-shaped focus 7. The X-ray source 2has an output of 1500 W within the optical distance 6 in which theobject 4 to be investigated is arranged.

[0060] The longitudinal alignment 8, i.e. the focus length (longitudinalextension) of the focus 7 is aligned along two boundary surfaces 5 ofthe object 4. For a required phase contrast, the condition sin α<<λ·L/D·s is aligned in which case the angle α corresponds to an angledeviation of the focus longitudinal direction of the tangential surfaceboundary that should be made visible, s is the focus length of thefocus, b the focus width of the focus, k the wave length of theX-radiation, L the optical distance between the focus of the X-raysource and the surface boundaries of the object and D a minimum distancebetween the surface boundaries 5 to be shown. The minimum distance Dbetween the surface boundaries to be shown corresponds to the spatialcoherence length 14. With λ=0,070 nm, s=2 μm, b=10 μm, L=1 m and D=1 μmit thus follows that b<<70 μm and a<<2°. In order to record the phasecontrast image, the focus width b is clearly less than 70 μm. For afocus length s of 2 mm the alignment is more exact than 20.

[0061] Focus 7 can easily be aligned if it is known how the boundarysurfaces 5 to be shown are oriented. If an orientation of the boundarysurfaces 5 to one another is unknown, several phase contrast images arerecorded to determine the optimum alignment. A good alignment can beseen in a clear phase contrast. The searched for boundary surfaces 5lead to clear borders of light and dark lines in the phase contrastimage.

EXAMPLE 2

[0062] Phase contrast X-ray device 1 with monochromator 18 as a gradientmultilayer reflector 20 with a planar area of reflection 27 (FIG. 4).

[0063] The gradient multilayer reflector 18 with a planar area ofreflection 27 is shown in FIG. 3. A periodic series of layers of twolayer types 22 (A) and 24 (B) is arranged on a substrate 21. The layertypes distinguish themselves in each case via a refractive index r_(A)and r_(B) and corresponding layer thicknesses d_(A) and d_(B). A totallayer thickness (total of the layer thicknesses d_(A) and d_(B))increases in a direction of propagation. The total d₂ exceeds the totald₁.

[0064] The gradient multilayer reflector 20 is arranged in theexcitation light path between the X-ray source 2 and the object 4 andfunctions as a monochromator 18. The X-radiation reflected from thereflector 20 apparently emerges from the mirrored (virtual) X-ray source3 and then hits the object 4 that is arranged within the opticaldistance 6. As a result, X-radiation of suitable spatial and temporalcoherence 14 and 15 passes through the object 4. The X-radiation passesthrough the object 4 to the evaluation unit 16. The evaluation unit 16has an X-ray film. The inference patterns resulting from the X-radiationpassing through the object via the surface boundaries 5 are made visibleon the X-ray film.

EXAMPLE 3

[0065] Phase contrast X-ray device 1 with monochromator 18 and analyzer19 as two gradient multilayer reflectors with planar areas of reflection27 (FIG. 5).

[0066] In addition to the preceding example, a further multilayerreflector is arranged 20 in the light path of the X-radiation 11 betweenthe object 3 and the evaluation unit 16. The object of the secondmultilayer reflector is that of an analyzer 19. Monochromator 18 andanalyzer 19 form a so-called monochromator analyzer set. Monochromator18 and analyzer 19 are arranged with areas of reflection 27 alignedparallel to one another. The analyzer 19 is designed in such a way thatnon-deflected X-radiation 12 arrives at the X-ray film of the evaluationunit 16 and is detected. X-radiation 13 deflected from object 4 is notreflected and does not reach the X-ray film.

[0067] Monochromator 18 and analyzer 19 have a gradient course d(x)along the direction of propagation x of the specific reflector that isaligned to the same source point 2 or its mirror images 3 and 3′ and thesame wave length L of the X-radiation 11. For a gradient multilayerreflector 20 with a planar area of reflection 27, the following appliesto the gradient course: d(x)=(λ/2)(x/a) with the wave length λ of theX-radiation and the distance a of the reflector 20 from the source pointof the X-ray source 2 (cf. Schuster et al., Proc. SPIE, 3767 (1999),pages 183-198). If the monochromator 18 is arranged within the distancea_(M) and the analyzer 19 within the distance a_(A) from the X-raysource 2, the following applies to the gradient course of themonochromator 18 d_(M)(x)=(λ/2) (x/a_(M)) and for the gradient course ofthe analyzer 19 d_(A)(x)=(λ/2)(x/a_(A)).

EXAMPLE 4

[0068] Phase contrast X-ray device 1 with monochromator 18 and analyzer19 as two gradient multilayer reflectors 20 with parabolic areas ofreflection 271 and 272 (FIG. 6).

[0069] The monochromator area of reflection 271 and the analyzer area ofreflection 272 are arranged opposite one another in such a way thattheir center lines 28 and 29 are aligned parallel to one another. Unlikethe preceding examples, the object 4 is in a parallel light path. Thegradient course of a gradient multilayer reflector with parabolic areasof reflection is described in Schuster et al., Proc. SPIE, 3767 (1999),pages 183-198.

[0070] The monochromator analyzer set is specifically tuned to aspecific wave length. Unlike the planar gradient multilayer reflectors,the wave length is hereby changed by replacing the monochromatoranalyzer set.

EXAMPLE 5

[0071] Phase contrast X-ray device 1 with monochromator 18 and analyzer19 as two gradient multilayer reflectors with elliptical areas ofreflection.

[0072] The gradient course of a gradient multilayer reflector withelliptical areas of reflection is described in Schuster et al., Proc.SPIE, 3767 (1999), pages 183-198.

[0073] In the same way as for gradient multilayer reflectors withparabolic areas of reflection, the monochromator analyzer set isspecifically tuned to a specific wave length. The wave length is alsochanged here by replacing the monochromator analyzer set.

EXAMPLE 6

[0074] Phase contrast X-ray device 1 with monochromator 18 and analyzer19 as two gradient multilayer reflectors with circular areas ofreflection.

[0075] Both reflectors 20 have sharp focal circles. The gradient coursesare tuned to the same wave length. The gradient course of a gradientmultilayer reflector with circular areas of reflection is described inSchuster et al., Proc. SPIE, 3767 (1999), pages 183-198.

[0076] In the same way as for gradient multilayer reflectors 20 withparabolic or elliptical areas of reflection, the monochromator analyzerset is specifically tuned to a specific wave length. The wave length canalso be changed here by replacing the monochromator analyzer set.

EXAMPLE 7

[0077] Phase contrast X-ray device with monochromator and analyzer astwo gradient multilayer reflectors with different areas of reflection.

[0078] Such an arrangement is then, for example, possible when the lightpaths are taken over in the focal points of the reflectors or as aparallel ray.

1. Phase contrast X-ray device (1) for creating a phase contrast image(17) of at least one object (4), with at least one X-ray source (2) forgenerating an X-radiation (11), that has a specific spatial coherence(15) within a specific optical distance (6) to the X-ray source (2), andat least one evaluation unit (16) for converting the X-radiation (12,13) after the X-radiation (11) has passed through the object (4)arranged within the optical distance (6) to the X-ray source (2) in thephase contrast image (17) of the object (4), characterized in that theX-ray source (2) shows an output ranging from 50 W up to and including10 kW and a spatial coherence length (14) of the X-radiation (11) hasbeen selected within the optical distance (6) to the X-ray source (2)ranging from 0,05 μm up to and including 10 μm.
 2. X-ray deviceaccording to claim 1 in which the X-ray source (2) has a line-shapedfocus (7).
 3. X-ray device according to claim 1 or 2 in which alongitudinal extension of the line-shaped focus (7) is aligned in thedirection towards the object (4).
 4. X-ray device according to one ofthe claims 1 to 3 in which the X-ray source (2) has an X-ray tube with atransmission anode.
 5. X-ray device according to one of the claims 1 to3 in which the X-ray source (2) has a parametric X-radiation source(PXR).
 6. X-ray device according to one of the claims 1 to 5 in whichthe X-radiation (11) has a specific temporal coherence (15).
 7. X-raydevice according to one of the claims 1 to 6 in which there is at leastone monochromator (18) for generating the temporal coherence (15) of theX-radiation (11).
 8. X-ray device according to one of the claims 1 to 7in which the evaluation unit (16) has at least one analyzer (19) foranalyzing the X-radiation (12, 13) after it has passed through theobject (4).
 9. X-ray device according to claim 7 or 8 in which themonochromator (18) and/or analyzer (19) has at least one gradientmultilayer reflector (20).
 10. X-ray device according to claim 9 inwhich the gradient multilayer reflector (20) has a periodic series oflayers of a first layer type A (22) and at least a further layer type B(24) in which case the first layer type A (22) has a first refractiveindex r_(A) and a first layer thickness d_(A) (23) and a further layertype B (24), a further refractive index r_(B) and a layer thicknessd_(B) (25) differing from the first refractive index r_(A) and in atleast one direction of propagation of the reflector (20), there is amonotone increase in layer thicknesses by a total of (d d_(A)+d_(B))(26).
 11. X-ray device according to claim 9 or 10 in which the gradientmultilayer reflector (20) has at least one area of reflection (27) fromthe elliptical and/or parabolic and/or planar and/or circular and/orhyperbolic group.
 12. Method for creating a phase contrast image of anobject by using a phase contrast X-ray device according to one of theclaims 1 to 11, with the following procedural steps: a) Arranging theobject within the optical distance to the X-ray source, b) X-radiationpassing through the object and c) Creating the phase contrast image fromwhere the X-radiation passes through an object by means of theevaluation unit.
 13. Method according to claim 12 in which theX-radiation forms an interference pattern after it has passed throughthe object that is detected for creating the phase contrast image. 14.Method according to claim 12 in which an X-radiation which is deflectedwhen passing through the object for creating the phase contrast imageand/or an X-radiation which is non-deflected when passing through theobject is detected.
 15. Method according to claim 14 in which thedeflected X-radiation and/or non-deflected X-radiation is selected bymeans of an analyzer with a gradient multilayer reflector.
 16. Methodaccording to one of the claims 12 to 15 in which several phase contrastimages are created by means of the X-radiation of different spatialcoherences that are processed to an overall phase contrast image bymeans of an image processing unit.
 17. Method according to claim 16 inwhich the optical distance between the object and the X-ray sourcevaries for generating the different spatial coherence.
 18. Methodaccording to claim 16 or 17 in which orientation of the object to thedirection of propagation of the X-radiation varies for generating thedifferent spatial coherence.
 19. Method according to one of the claims12 to 18 in which an object that, in essence, consists of a materialwith a low absorption coefficient for the X-radiation is used. 20.Method according to one of the claims 12 to 19 in which many phasecontrast images of the object are created to generate a phase contrastcomputer tomogram of the object.